Ok, I would like to know more about heads and cams.

I was looking at some ads for roller rockers and roller hydrolic lifters. Why are these better.

Would a set of roller rockers (aluminum) fit on my set of 416 heads? Would the provide a benefit?

What is a roller cam compared to a normal cam?

Thanks.

 

DISCLAIMER: I am no expert but:

As far as I know the advantage of roller rockers is less resistance. Additionally you can get different ratio rockers than what you currently have to give you a little extra lift.

The roller cams are better because of less friction and also because they allow a steeper ramp which opens and shuts the valves faster. This also allows the valve to stay open longer.

I am sure there are roller rockers available to fit your heads but I do not have the part numbers. Also they have full roller rockers and roller tip rockers as well. (they are a little cheaper but do not have all of the advantages)

just an opinion - but hope it helps

 

That was the other question i forgot, whats the difference between the 1.50, 1.60 and the other "ratios" and what is the ratio for?

 

When you raise the ratio of a rocker (i.e. from 1.5 > 1.6) you are effectively increasing the lift of your cam. I'm not sure the exact amount, but it is in fact a very noticeable difference. Sometimes you have to make adjustments for this, sometimes not.

 

There is not a 1:1 ratio for cam lift to valve lift or opening.
If you look at your rockers you will see that the "arm" going to the valve is longer. If the fulcrum were in the center of the rocker you would have your 1:1 ratio of cam lift to valve lift. But since the fulcrum is offset you end up with more actual valve lift than the lift your cam advertises. The amount of lift is the ratio number that you see (1.5 1.6 etc) so a higher ratio rocker will give you more lift.
I do not think it works out to be EXACTLY this way, but take your advertised cam lift and multiply by the rocker ratio (1.5) and you should come pretty close to what your valve lift is.
I am using the term "lift" kind of generically here, but I am trying to keep it simple.

- Z

 

I understand. So would going to a higher ratio be better or worse, or does it depend on my setup?

 

It depends on your setup. You need to make sure you have the clearance to go to higher ratio rockers and you also need to make sure your springs can handle it. I think I also remember something about needing screw in studs to go to higher ratio's but I would not rely on just my word for it as I do not remember exactly.

- Z

 

Yea, this topic will take you hours. There is a ton of info. It's like asking for a compilation of MAF stuff. Try one of those searches with Vader's name in it a few times. Lots of reading, you'll never get it all out of this thread, nor probably out of this board.

 

Yep, Devil is correct. This is just one of those toics that could go on eternally. If you perform a search, i know i've gone over some of the basics, i know RB83L69 has, Vader has, five7kid, ede, and a whole slew of others has.

 

I just read on one of the major cam makers website that going from a 1.5 rocker ratio to a 1.6 rocker ratio is like adding 2 to 4 degrees to your cam. I'am installing the 1.6 rockers on the intake side of my ZZ4 cam. I will leave the exhaust side at 1.5. By the way I have Trick Flow heads. Allen

 

Wha...? The change in rocker arm lengths does not do a thing to the duration AFAIK. It adds to the lift of the cam. 1.5 * .5 = .750 lift, 1.6 * .5 = .800 lift. The rocker isn't going to change the profile of the cam.

If I screwed that up I blame RB, he made me spill my coffee at work!!

 

I thought that generally when people mixed 1.5 and 1.6 they put the 1.6 on the exhaust side. Course, I guess this would vary by your cam.

 

Red Devil if you are refering to my post I did not say it added to the duration. I said the effect was "like" adding two to four degrees to the cam. Like you said it is caused by the added lift. I believe the information is on the Comp Cams website.

ljnowell

My cam is the ZZ4. It has a lift of .474 on the intake and .510 on the exhaust. Duration is 208 @.050 on the intake and 221 @.050 on the exhaust. You can see with reasonable flowing heads it can use more help on the intake side. That is why the 1.6 rockers on the intake side. The exhaust is just fine with 1.5 rockers. Allen

 

You are all correct, to a point, on the duration part. However, the details are in the fine print.

Nothing can change the advertised duration of the cam, as that is ground into it. However, .050" duration (.050" of tappet lift or .075" of valve lift, "standard" 1.5 ratio) will have a slight change. It will only be about 2° or so with an aftermarket cam. Is what happens is as the cam rotates, it transfers lift to the tappet, which goes up. The rocker arm multiplies that lift by the preset ratio and transfers that to the valve. by increasing the rocker ratio, you decrease the amount of time it takes for the valve to reach .075" of lift. By decreasing the time it takes to get there, you in effect, raise the .050" duration. So as you can see, it does and it doesnt effect cam duration. But, for the most part, the main thing about higher rocker ratios is the increase in lift, not duration. Generally, the steeper the ramp rates, the more of an increase you will see with the added rocker ratio. This is why the peanut cam responds so well. I think the overall .050" duration of the peanut cam has an effective change of mid to high 3.xx°.

To get the lift at the valve, multiply the lobe lift by the rocker ratio.

EX: .350 (lobe lift) x 1.5 (rocker ratio) = .525 valve lift

To change from 1.5 ratio to 1.6, divide by the current valve lift (brings to to lobe lift) then multiply by 1.6.

EX. [.525 (valve) / 1.5 (ratio) ] x 1.6 (new ratio) = .560 (new valve lift)

 

Either I'm to lazy to read or its not there. What kinda ride do you have? Interesting thing to keep in mind, my car came stock with a roller cam and roller lifters. I dont belive someone just threw those in there. Its an 89bird 305, came with TBI but I went with a carb. If someone knows the date of when roller cams were given to the 3rd gen F bodys you would be like.. the history *** so, Speak up!

Another question on the topic, my brother speaks of some... 20-30HP gain simply by switching to roller lifters. Maybe this is possible if it changes up the ratio and all that but I have my share of study to complete on that. So.. Under 200 bucks you can gain another 20-30?

 

87-up was the change over for cars for flat tappet to roller

96 was the year for trucks i beleive.

 

Roller lifters require a roller cam. If he tries that with a flat tappet cam he'll have a lot of broken junk in his engine.

Changing from flat tappet to a complete roller system will allow you to run a more radical cam without effecting the engine's low speed driveability. So, all other things being equal, you can definitely get more hp from a roller cam but it costs a lot of $$$, certainly more than $200 for a changeover.

If you already have a roller setup then there are a lot of cams out there which will work much better than the factory cam. LT1 cams can be had for $50 or less on eBay.

Many of the old hands will tell you to work on your heads instead, i.e., port and polish, which is worth a good 30 hp on an average 305/350 smallblock. When the heads are optimized EVERYTHING else will work to its best potential. Good advice, IMHO.